In recent years, many electronic devices such as mobile phone terminals are equipped with a touch panel as an input device for accepting an input operation by a user. In such a type of electronic devices, a transparent touch panel is provided over a screen of a display section (such as an LCD (Liquid Crystal Display) or an organic EL (Electroluminescence) display) for allowing a user to perform an intuitive operation. Accordingly, each position on the screen can be made to correspond to an operating position on the touch panel. In other words, by touching a desired operation target (an object such as a button or an icon) directly with a finger, an instruction for operating the corresponding object can be issued in such an electronic device.
Besides, the technology of a touch panel has been developing in these years, and in addition to a touch panel in which a touch operation is detected as an input operation by a user, a touch panel in which proximity of a user finger is detected as an input operation by a user has been developed. As the touch panel in which proximity of a finger is detected, for example, a non-contact type user input device disclosed in Patent Document 1 is known.
The non-contact type user input device disclosed in Patent Document 1 has the following configuration. The non-contact type user input device includes a plurality of linear transmitting electrodes, a transmitter for supplying a transmission AC current to each of the transmitting electrodes, a plurality of linear receiving electrodes disposed so as not to be in contact with the transmitting electrodes, and a receiver for receiving an AC current flowing through each receiving electrode. A capacitor is formed on each of intersectional points between the transmitting electrodes and the receiving electrodes, and the electrostatic capacity of the capacitor is varied in accordance with the degree of proximity of a fingertip. Accordingly, on the basis of the variation of the electrostatic capacity, the non-contact type user input device can recognize a distance between the touch panel and the finger.